here in boston, the ones in my neighborhood:
VW Golf
Saab 9-3
VW Beetle (more than most all else)
BMW/Mini Cooper
and Saturn
those seem to be the geek gays though b/c you also will see the geek stickers with them as well.
that said, I have a Saab and I'm not gay... although one of my friends is gay and he also has a Saab... maybe I'm just repressing it.